Circuit board microprocessors often require some form of protection from radiated RF emissions that may be in proximity to their location. Typically, this has been accomplished by providing a thin metallic box or lid style cover that is soldered to a printed circuit (PC) board over one or more electronic components that require the shielding. As best seen in prior art FIG. 1, the shield 100 generally includes tabs 101, 103, spaced at intervals, such that the tabs are positioned into slots located in the circuit board. Each shield generally uses several twist style tabs 105 that are soldered to a PC board (not shown). These tabs work to prevent any long gaps between the bottom of the shield and the PC board since any gaps may allow penetration of RF energy into the protected area. Thus, even with the development of the metallic shielding system, each shield must be individually configured to reduce the probability of any leakage into the protected area for eliminating these types of gaps.
In use, the shield 100 requires insertion into slots/holes in the PC board where, if not locked in place, can raise above the PC board during the soldering process. In cases where repair or inspection of the shielded electrical components are required, the shield must be de-soldered and removed to allow access to that area of the PC board assembly. The current solution for this situation is a metal frame sometimes referred to as a “fence” that is soldered to the PC board with a snap-on type lid. However, in this configuration, two component parts are required to form the shield assembly. Although somewhat effective, this type of shielding arrangement can significantly increase component and production costs to the extent they may be only be used only in specialized shielding situations.
In addition, during the repair process, these types of snap-on lids are typically discarded and a new lid is installed in order to prevent problems with the lid coming loose thereby creating a mechanical rattle. As seen in prior art FIG. 2, the fence 200 includes a cross bar style support 201, 203, which must be mechanically snipped away if a repair is required prior to the installation of a new lid. This type of fence 200 further includes a plurality of engagement slots 205, 207 as well as a plurality of projections 209, 211 that engage with the PC board to hold the fence into position. One or more twist tabs 213 are also used to provide a firm mechanical connection to portions of the PC board. Hence, as current PC board assemblies migrate to primarily surface-mount devices (SMDs), these types of RF shield assemblies also must adapt to this process. Although some shielding solutions have been developed strictly for surface-mount processing, these solutions have issues relative to providing an adequate seal against the circuit board in view of component size limitations.
Any type of RF shield is used in connection with outside connector-type devices used on the PC board. Shields that are designed for covering or providing a hood, are often referred to as a “dog house” shield and are used for isolating the pins of a connector body that provide external connections to the outside devices. The necessity for added holes in the PC board and the typical assembly techniques employed to attach the shield components with twist tabs prior to the solder operation adds expensive assembly time and limits the application to a leaded style component parts. Additionally, these types of connector shields utilize fastening screws to mechanically provide a strain relief for the connector as well as enabling a adequate electrical ground. Thus, shields of this type also add a great deal of operational cost in view of these complex assembly requirements.
Moreover, as seen in prior art FIGS. 3A and 3B, some types of connector shields also incorporate ground features that include additional shielding added through a weld or fastening operation for providing a compression contact to a case or chassis. FIG. 3A illustrates a perspective view of connector shield 300 having a frame 301 that includes a ground slot 303 for insertion of a grounding member (not shown) that provides an electrical ground. A grounding tab 305 and fastening tab 307 are also used to hold the connector shield to a PC board or the like. Similarly, FIG. 3B also illustrates a perspective view of an alternative bracket similar to that in FIG. 3A, where a frame 309 includes a ground spring 311 for making ground contract with a metallic object and one or more twist tabs 313 for grounding the frame 309 to a PC board. Those skilled in the art will recognize that any wide gaps in a case and/or chassis can be a potential problem for RF emissions, such that metallic foils and metal tapes are also applied to these types of connectors in order to isolate a port from any radiated RF emissions. In that these types of shields are inadequate for shielding electrical components from RF energy, a new type of shield is required for these applications.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.